The invention relates to the field of tamper detecting devices for electricity, gas, or water meters or the like, and more particularly to an arrangement for detecting removal of such a meter from its socket and giving an indication thereof which is relatively immune to being bypassed or subverted.
Various techniques have been used to prevent and/or detect tampering with a meter that measures a billable quantity such as electricity, gas or water. These techniques generally take the form of either special locks or seals for preventing removal of the metering apparatus from its associated socket, or devices for visually indicating that the meter has been removed or replaced in its socket.
Exemplary of this latter category are various types of warning flags, lights or other visual indicators which are actuated upon the removal or reinsertion of the meter from its socket. Such arrangements are shown, for example, in U.S. Pat. Nos. 4,386,313 and 4,386,314. It is also known to optically encode a warning flag using a so-called "bar code" as shown in copending U.S. Patent Application Ser. No. 489,895, filed Apr. 29, 1983, entitled "Optically Encoded Tampering Indicator for Display Register" and assigned to the same assignee as the present application. As disclosed by this application, the bar coding of a tamper indicating flag enables automatic remote optical detection of the flag to be performed by the meter reader or inspector using a commercially available laser scanner.
However, the above arrangements suffer from the disadvantage of requiring fairly complex actuating mechanisms which, once their method of operation is known, can be bypassed or subverted by relatively simple means.
It is therefore a primary object of the present invention to provide a simple and economical arrangement for indicating if a metering apparatus has been moved relative to its socket, and which is highly immune to either physical or electronic subversion.